Influence of repeated daily menthol exposure on human temperature regulation and perception

Abstract

A single exposure to menthol can, depending on concentration, enhance both cool sensations and encourage body heat storage. This study tested whether there is an habituation in either response after repeated-daily exposures. Twenty-two participants were assigned to one of three spray groups: Control (CON; n=6), 0.05% L-menthol (M(0.05%); n=8), and 0.2% L-menthol (M(0.2%); n=8). On Monday (20°C, 50% rh) participants were sprayed with 100 mL of solution and undertook 40 min of cycling at 45% of their peak power (Ex1), from Tuesday to Thursday (30°C, 50% rh) they were sprayed twice daily whilst resting (R1 to R6), Friday was a repeat of Monday (Ex2). Thermal sensation (TS), thermal comfort, perceived exertion, irritation, rectal and skin temperature (Tsk), skin blood flow (SkBF) and sweat rate were monitored. A two-way ANOVA (alpha=0.05) compared responses from the beginning (Ex1, R1) and end (Ex2, R5) of the testing week. M(0.2%) induced significantly (P<0.05) cooler TS at the beginning of the week (Ex1, R1) compared to the end (Ex2, R5), indicating habituation of TS; this was not observed in M(0.05%). No other perceptual or physiological responses habituated. 0.2% Menthol caused a heat storage response, mediated by vasoconstriction, at the beginning and end of the week, suggesting the habituation of TS occurred in a pathway specific to sensation. In summary, the cooling influence of 0.2% menthol habituates after repeated-daily exposures, but with no habituation in heat storage.

Current Knowledge on the Vascular Effects of Menthol

“…Menthol gels (0.5, 4.6, 10%) cause skin temperature reduction irrespectively of concentration (Lasanen et al, 2016), which may be explained by an increase in evaporative heat loss induced by the formulation ethanol (10%). A similar explanation seems to match the observed decrease in skin microcirculatory perfusion after spraying menthol (0.05, 0.2%) on the torso and upper limbs (Jason Gillis et al, 2015). Similarly, the application of menthol (10 mg/kg of body weight) on the neck, arm and leg evokes perfusion reduction on the hallux (Valente et al, 2015).…”

“…Evidence for the existence of menthol-evoked heat-conservation responses comes from studies reporting that menthol lowers temperature thresholds for virtually all the thermoregulatory responses to cooling (Kozyreva et al, 2010), which are attributed to TRPM8 channel activation (Camila Almeida et al, 2012). In humans, application of a menthol spray on the upper body results in a vasoconstriction response on finger microcirculation (Jason Gillis et al, 2015). Furthermore, whole-body application results in a slower decrease of rectal temperature comparing with cool water immersion, which was again attributed to peripheral vasoconstriction (Kounalakis et al, 2010) even though perfusion was not assessed.…”

l-Menthol attenuates the magnitude of cold-induced vasodilation on the extremities of young females

“…Thanks to its cooling effect on the skin, it is widely used in after sun creams, lotions, and pain killers. Likewise, so far, research on the effect of intervention of l -menthol on the thermoregulatory system tends to be concentrated on heat stressed conditions due to its perceptual cooling effect [ 20 , 21 ]. However, menthol is an agonist of the TRPM8 channel, which serves as a cutaneous thermosensor activating several cold-defense responses [ 14 , 22 ].…”

“…Previous studies where researchers used menthol as attenuating substances of perceptual heat strain tended to use l -menthol in concentration of 0.8% [ 20 ]. 0.05% menthol induced cool sensations [ 27 ], and 0.2% menthol enhances not only coolness but heat storage [ 21 ]. The 1.5% concentration of this study is thought to be an adequate concentration to arouse thermoregulatory changes without pronounced irritation when it is applied only to the forearm.…”

Effects of Intermittent Neck Cooling During Repeated Bouts of High-Intensity Exercise

“…Actual temperature changes are not required to alter thermoregulatory responses or to improve performance [ 7 ]. We chose to globally account for both actual and perceived cooling by including a treatment group that received an over-the-counter spray (SPRAY) containing menthol, a substance that interacts with cold receptors in sensory neurons [ 6 ] and alters exercise performance [ 5 , 23 ]. Recent evidence suggests an L-menthol spray with a concentration of 0.2% lowers TS [ 23 ].…”